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Extracting HDR Gain Map from iOS 14.1+ (iPhone 12+) photos
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import UIKit | |
import MobileCoreServices.UTCoreTypes | |
if #available(iOS 14.1, *) { | |
let input = Bundle.main.url(forResource: "IMG_0037", withExtension: "HEIC")! | |
let output = FileManager().temporaryDirectory.appendingPathComponent("IMG_0037.GAIN_MAP.BMP") | |
let source = CGImageSourceCreateWithURL(input as CFURL, nil)! | |
// urn:com:apple:photo:2020:aux:hdrgainmap | |
let dataInfo = CGImageSourceCopyAuxiliaryDataInfoAtIndex(source, 0, kCGImageAuxiliaryDataTypeHDRGainMap)! as Dictionary | |
let data = dataInfo[kCGImageAuxiliaryDataInfoData] as! Data | |
let description = dataInfo[kCGImageAuxiliaryDataInfoDataDescription]! as! [String: Int] | |
let size = CGSize(width: description["Width"]!, height: description["Height"]!) | |
let ciImage = CIImage(bitmapData: data, bytesPerRow: description["BytesPerRow"]!, size: size, format: .L8, colorSpace: nil) | |
let cgImage = CIContext().createCGImage(ciImage, from: CGRect(origin: CGPoint(x: 0, y: 0), size: size))! | |
let destRef = CGImageDestinationCreateWithURL(output as CFURL, kUTTypeBMP, 1, nil)! | |
CGImageDestinationAddImage(destRef, cgImage, [:] as CFDictionary) | |
CGImageDestinationFinalize(destRef) | |
print(output) | |
} |
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Just to report back on this. I have managed to get the HDRGainMap from a
AVCapturePhoto
with the following:The key thing was that the capture device was configured correctly. From an Apple DTS Engineer:
The last hurdle I'm encountering is that this still returns
nil
on an iPhone 13. I'm assuming the older hardware does not support it, but it's strange because I can access some sort of HDRGainMap via theCGImageSourceCopyAuxiliaryDataInfoAtIndex(source, 0, kCGImageAuxiliaryDataTypeHDRGainMap)! as Dictionary
method with a photo captured by the default camera app on the iPhone 13. It does appear different to the iPhone 16 Pro however, so I assume there is some difference in hardware output. See below: